JP4793321B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine that supplies a part of exhaust gas taken out from an exhaust passage of the internal combustion engine as EGR gas into a cylinder.

  An internal combustion engine that is applied to an internal combustion engine in which two intake ports are provided for one cylinder and that can supply EGR gas into the cylinder through only one of the two intake ports. An exhaust gas recirculation device is known (Patent Document 1). In addition, Patent Documents 2 to 5 exist as prior art documents related to the present invention.

Japanese Patent Laid-Open No. 5-18254 JP 2004-34006 A Japanese Patent Laid-Open No. 11-303687 JP 2002-89377 A JP 2004-270622 A

  In the apparatus of Patent Document 1, EGR gas is supplied to one cylinder via one intake port and air is supplied via the other intake port. Therefore, the temperature of the EGR gas and the air If the temperature difference from the temperature changes, the distribution of EGR gas in the cylinder may change, leading to deterioration of combustion.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas recirculation device for an internal combustion engine that can mitigate a change in temperature difference between EGR gas supplied to a cylinder and air and suppress deterioration of combustion.

An exhaust gas recirculation device for an internal combustion engine according to the present invention is applied to an internal combustion engine in which a plurality of intake ports are provided for one cylinder, and a part of exhaust gas taken out from an exhaust passage of the internal combustion engine is supplied to the plurality of intake ports. In the exhaust gas recirculation apparatus for an internal combustion engine that can supply EGR gas into the cylinder through only a part of the intake ports, the EGR gas supplied to the cylinder through only the part of the intake ports an EGR gas temperature adjusting means capable of adjusting the EGR gas supply temperature is a temperature, the temperature of the air supplied to the cylinder via the remaining intake port of said intake port and said EGR gas supply temperature Target setting means for setting a target temperature of the EGR gas supply temperature so that the temperature difference falls within a predetermined range; and the EGR gas supply temperature is set to the target setting. As becomes the target temperature set by the stage, to solve the problems described above by providing, an EGR gas temperature control means for controlling the EGR gas temperature control means (claim 1).

According to the exhaust gas recirculation system of the present invention, the target temperature of the temperature difference between the temperature of air supplied to the EGR gas supply temperature and the cylinder of the EGR gas supplied into the cylinder is set so as to fall within a predetermined range Since the EGR gas supply temperature is controlled, the change in the temperature difference between the EGR gas supplied into the cylinder and the air can be mitigated. As a result, deterioration of combustion when EGR gas is supplied into the cylinder can be suppressed.

  The EGR gas temperature adjusting means can be realized in various modes as long as the EGR gas supply temperature can be adjusted. For example, a cooling device capable of exchanging heat between the EGR gas and the refrigerant is provided, a bypass passage capable of bypassing the cooling device is provided, and an EGR gas supply temperature is adjusted by adjusting an inflow amount of the EGR gas passing through the bypass passage. You can also The EGR gas temperature control means further includes an exhaust gas recirculation passage connected to the exhaust passage, and fuel supply means capable of injecting fuel into the exhaust gas recirculation passage is provided as the EGR gas temperature adjustment means. The means may control the fuel supply means so that fuel is injected into the EGR passage when the EGR gas supply temperature is higher than the target temperature (Claim 2). In this case, the fuel supply means injects the fuel and vaporizes the injected fuel in the exhaust gas recirculation passage, whereby the EGR gas flowing in the exhaust gas recirculation passage can be cooled using the latent heat of vaporization. When using the latent heat of vaporization, the time required for vaporization of the fuel is short, so that the EGR gas can be cooled in a shorter time than when the EGR gas is cooled using heat exchange with the refrigerant. Therefore, according to this aspect, the EGR gas supply temperature can be controlled with good responsiveness.

  The fuel supply amount to be injected by the fuel supply means may be set appropriately. For example, a plurality of candidates for the fuel supply amount to be injected by the fuel supply means are extracted from the exhaust passage based on a required temperature decrease amount required to reduce the EGR gas supply temperature to the target temperature. The fuel supply means calculates the minimum value among the candidates calculated by the candidate calculation means and the candidate calculation means calculated based on the temperature of the exhaust gas recirculation passage based on the passage wall temperature at a predetermined position of the exhaust gas recirculation passage. And a fuel supply amount calculating means for calculating the fuel supply amount to be injected. As the amount of fuel vaporized increases, the temperature drop range of the EGR gas increases. However, if the fuel supply amount exceeds the appropriate amount, the fuel that has not been vaporized adheres to the passage wall of the exhaust gas recirculation passage, thereby May cause clogging. According to this aspect, since the minimum value among the plurality of candidates is calculated as the fuel supply amount, it is possible to prevent the fuel supply amount from becoming excessive from an appropriate amount. Thereby, it becomes possible to avoid clogging of the exhaust gas recirculation passage due to fuel adhering to the passage wall. In this aspect, there may be further provided a fuel supply prohibiting means for controlling the fuel supply means so that fuel injection by the fuel supply means is prohibited when the passage wall temperature of the exhaust gas recirculation passage is a predetermined value or less. (Claim 4). In this case, since the fuel injection is forcibly prohibited when the passage wall temperature is equal to or lower than a predetermined value, it is possible to reliably avoid clogging of the exhaust gas recirculation passage.

  In one aspect of the exhaust gas recirculation apparatus of the present invention, the internal combustion engine is configured as a compression ignition type engine having a fuel injection valve for injecting fuel into the cylinder, and fuel injection by the fuel supply means is performed. When the EGR gas supply temperature is within an allowable range including the target value after the ignition, a predetermined operation that can prevent the ignition timing of the fuel injected by the fuel injection valve from being advanced is applied to the internal combustion engine. Further, an early ignition preventing means may be further provided (claim 5). The fuel injected by the fuel supply means is vaporized and then supplied into the cylinder together with the EGR gas. Therefore, before the fuel is injected into the cylinder by the fuel injection valve, the fuel concentration in the cylinder becomes high and the ignition timing in the compression stroke is advanced, so that the exhaust performance compared with the normal time when fuel is not supplied by the fuel supply means May deteriorate, that is, harmful components in the exhaust gas may increase. According to this aspect, since the predetermined operation that can prevent the ignition timing from being advanced is performed on the internal combustion engine, it is possible to prevent the exhaust performance from being deteriorated due to the fuel injection by the fuel supply means. The predetermined operation may be an operation that can prevent the ignition timing from being advanced.

  For example, the internal combustion engine may divide fuel injection by the fuel injection valve into main injection performed at a predetermined time and pilot injection performed before the predetermined time with a smaller amount of fuel than the main injection. The injection mode can be executed, and the fuel injection timing and the fuel injection amount of each of the main injection and the pilot injection can be changed. At least one of an operation of reducing the fuel injection amount of the pilot injection and an operation of retarding the fuel injection timing of the main injection may be performed on the internal combustion engine. Since both the operation of reducing the fuel injection amount of the pilot injection and the operation of retarding the ignition timing of the main injection have the effect of suppressing the early ignition timing, both of these operations may be performed.

  In one aspect of the exhaust gas recirculation apparatus of the present invention, the internal combustion engine is configured as a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into the cylinder, and fuel injection by the fuel supply means is performed. If the EGR gas supply temperature exceeds the upper limit of the allowable range including the target value after being performed, the distribution of the air-fuel mixture formed in the cylinder by the fuel injected from the fuel injection valve is supplied to the cylinder. The system may further comprise a distribution change preventing means for executing a predetermined operation on the internal combustion engine that can prevent the EGR gas and the intake air from changing with a temperature difference. When the EGR gas supply temperature exceeds the upper limit of the allowable range, the relatively high temperature EGR gas is biased toward the center in the cylinder due to the temperature difference between the EGR gas supplied to the cylinder and the air. As a result, the temperature of the atmosphere in the center of the cylinder rises, so that the evaporation of the fuel spray injected from the fuel injection valve is accelerated. This makes it difficult for the air-fuel mixture to reach the vicinity of the inner peripheral surface of the cylinder and changes the distribution of the air-fuel mixture formed in the cylinder. That is, harmful components in the exhaust gas may increase. According to this aspect, since the predetermined operation that can prevent the change in the distribution of the air-fuel mixture is performed on the internal combustion engine, it is possible to prevent the exhaust performance from deteriorating due to the fuel injection by the fuel supply means. The predetermined operation may be any operation that can prevent a change in the mixture distribution.

  For example, the internal combustion engine can change the fuel injection pressure by the fuel injection valve, and the fuel injection by the fuel injection valve is performed at a predetermined timing with a main injection performed at a predetermined timing and a smaller amount of fuel than the main injection. The pilot injection mode can be executed to divide into pilot injection performed before, and each fuel injection timing and each fuel injection amount of the main injection and the pilot injection can be changed, The distribution change preventing means retards the operation of increasing the fuel injection pressure by the fuel injection valve, the operation of decreasing the fuel injection amount of the pilot injection, and the fuel injection timing of the main injection as the predetermined operation. At least one of the operations may be performed on the internal combustion engine (claim 8). The operation of increasing the fuel injection pressure by the fuel injection valve, the operation of decreasing the fuel injection amount of the pilot injection, and the operation of delaying the fuel injection timing of the main injection all have the effect of suppressing changes in the mixture distribution. Therefore, all of these operations may be performed, or two operations selected from these operations may be performed.

  In one aspect of the exhaust gas recirculation apparatus of the present invention, the internal combustion engine is configured as a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into the cylinder, and the gas flowing through the exhaust gas recirculation passage is arranged. An adjustment valve capable of adjusting the flow rate, and a passage wall temperature control means for controlling the adjustment valve to open when the engine speed of the internal combustion engine is decelerating and fuel injection by the fuel injection valve is interrupted. Furthermore, you may provide (Claim 9). According to this aspect, since the air passing through the cylinder is guided to the exhaust gas recirculation passage when the regulating valve is controlled to open, the temperature of the passage wall of the exhaust passage can be lowered. The opening on the opening side of the regulating valve may be determined as appropriate. For example, the regulating valve may be controlled to be fully opened.

  In this aspect, the internal combustion engine includes a compressor provided in an intake passage including the remaining intake port, a turbine provided in the exhaust passage downstream of a position where the exhaust recirculation passage is connected, A variable capacity turbocharger having a movable member capable of restricting an inlet of the turbine by moving between a maximum opening and a minimum opening, and the compressor and the turbine are combined so as to be integrally rotatable. A charger is provided, and the passage wall temperature control means is configured such that when the engine speed of the internal combustion engine is decelerating and fuel injection by the fuel injection valve is interrupted, the adjustment valve is fully opened, and You may control the said adjustment valve and the said movable member, respectively so that the opening degree of a movable member may become a close side (Claim 10). In this case, since the back pressure, which is the pressure in the exhaust passage upstream of the turbine, is increased by controlling the opening of the movable member to the closed side, the differential pressure between the inlet and outlet of the exhaust gas recirculation passage can be increased. . Thereby, the air passing through the exhaust gas recirculation passage can be increased.

  In the internal combustion engine, the internal combustion engine is provided in the exhaust passage downstream of the position where the compressor provided in the intake passage including the remaining intake port and the exhaust gas recirculation passage are connected. And a movable member capable of restricting the inlet of the turbine by moving between a maximum opening and a minimum opening, and the compressor and the turbine are combined so as to be integrally rotatable. A capacity-type turbocharger is provided, and the passage wall temperature control means opens the regulating valve when the engine speed of the internal combustion engine is decelerating and fuel injection by the fuel injection valve is interrupted. And the adjustment valve and the movable member may be controlled so that the opening degree of the movable member is on the open side. In this case, since the supercharging pressure, which is the pressure in the intake passage, is reduced by controlling the opening of the movable member to the open side, the differential pressure between the inlet and the outlet of the exhaust gas recirculation passage can be increased. Thereby, the air passing through the exhaust gas recirculation passage can thereby be increased.

  In one aspect of the exhaust gas recirculation apparatus of the present invention, the EGR gas temperature control means has the EGR gas cooled by the fuel injected by the fuel supply means reaches the cylinder via the partial intake port. The fuel injection timing by the fuel supply means may be controlled so that the arrival time is synchronized with the intake stroke of the cylinder. If the cooled EGR gas stays in the exhaust gas recirculation passage until it is supplied into the cylinder, the cooled EGR gas receives heat from the wall of the exhaust gas recirculation passage, etc., and the temperature of the cooled EGR gas rises. Resulting in. When a large amount of fuel is injected from the fuel supply means in order to avoid such a temperature rise, the fuel injection amount increases. According to this aspect, the EGR gas supplied to the cylinder can be targeted and cooled, and as a result, fuel injection by the fuel supply means becomes intermittent. As a result, the fuel consumption is suppressed, and the cooling efficiency of the EGR gas is improved.

As described above, according to the present invention, the temperature difference between the temperature of air supplied to the EGR gas supply temperature and the cylinder of the EGR gas supplied into the cylinder is set so as to fall within a predetermined range Since the EGR gas supply temperature is controlled to the target temperature, the change in the temperature difference between the EGR gas supplied into the cylinder and the air can be mitigated. As a result, deterioration of combustion when EGR gas is supplied into the cylinder can be suppressed.

(First form)
FIG. 1 shows a main part of an internal combustion engine to which an exhaust gas recirculation apparatus according to an embodiment of the present invention is applied. The internal combustion engine 1 is mounted on a vehicle (not shown) as a driving power source, and is configured as an inline 4-cylinder compression ignition type diesel engine in which four cylinders 2 are arranged in a row. Each cylinder 2 is provided in the engine body 3, and a piston (not shown) is provided in each cylinder 2 so as to freely reciprocate. The reciprocating motion of the piston is converted into the rotational motion of the crankshaft 4 and output. On the ceiling surface of each cylinder 2, a fuel injection valve 5 is provided at the center of the cylinder 2 so that its tip faces the cylinder 2. The fuel injection valve 5 is connected to a common rail (not shown) and is supplied with fuel of a predetermined fuel pressure.

  An intake passage 6 and an exhaust passage 7 are connected to each cylinder 2. The intake passage 6 includes two intake ports 8 and 9 provided for each cylinder 2, a first intake manifold 10 to which each intake port 8 is connected, and a second intake manifold 11 to which each intake port 9 is connected. And a communication passage 12 for communicating these intake manifolds 10 and 11. On the other hand, the exhaust passage 7 includes two exhaust ports 13 provided for each cylinder 2 and an exhaust manifold 14 to which each exhaust port 13 is connected. The intake ports 8 and 9 are opened and closed by an unillustrated intake valve, and the exhaust ports 18 are opened and closed by an unillustrated exhaust valve. The intake valve and the exhaust valve are driven to open and close by a valve gear (not shown) so that the opening / closing timing of each cylinder 2 is shifted by 180 ° CA with respect to the crank angle.

  The internal combustion engine 1 is provided with an open / close valve 15 that opens and closes the communication passage 12. When the communication passage 12 is closed by the on-off valve 15, the air guided to the intake passage 6 is guided to the first intake manifold 10 and then supplied into the cylinder 2 only through the intake port 8. On the other hand, when the communication passage 12 is opened by the on-off valve 15, the air guided to the intake passage 6 is guided to each of the first intake manifold 10 and the second intake manifold 11, and then the two intake ports 8, 9 is supplied into the cylinder 2 via the line 9. When a predetermined gas is sucked through the two intake ports 8 and 9, a swirl swirling in a plane intersecting the center line is generated in the cylinder 2. , 9 are configured.

  The internal combustion engine 1 is provided with an exhaust gas recirculation device 16 that supplies a part of the exhaust gas taken out from the exhaust passage 7 as EGR gas into the cylinder 2. The exhaust gas recirculation device 16 includes an exhaust gas recirculation passage 17 that connects the exhaust manifold 14 and the second intake manifold 11, an exhaust gas recirculation valve 18 that can adjust the flow rate of gas flowing through the exhaust gas recirculation passage 17, and an exhaust gas recirculation passage. 17 and a cooling device 19 for cooling the gas flowing through 17. The EGR gas is taken out from the exhaust passage 7 by opening the exhaust gas recirculation valve 18 while the communication passage 12 is closed by the on-off valve 15 described above. The EGR gas is supplied to each cylinder 2 via the exhaust gas recirculation passage 17, the second intake manifold 11 and the intake port 9 without being mixed with air. That is, the exhaust gas recirculation device 1 can supply the EGR gas into the cylinder 2 via only the intake port 9. The two intake ports 8 and 9 correspond to a plurality of intake ports according to the present invention, the intake port 9 corresponds to some intake ports according to the present invention, and the intake port 8 corresponds to the remaining intake ports according to the present invention. To do. When the exhaust gas recirculation valve 18 is opened while the communication passage is opened by the on-off valve 15, the EGR gas taken out from the exhaust passage 7 passes through the two intake ports 8 and 9 and enters the cylinder 2. To be supplied. In the following description, the state where the communication path 12 is closed by the opening / closing valve 15 may be referred to as a one-port via state.

  Further, the exhaust gas recirculation device 16 is a fuel supply means that can inject fuel into the exhaust gas recirculation passage 17 in order to adjust the temperature (EGR gas supply temperature) when the EGR gas is supplied into the cylinder 2 via a single port. The fuel addition valve 20 is further provided. A fuel having a predetermined fuel pressure is supplied to the fuel addition valve 20. The fuel is injected into the exhaust passage 17 by the fuel addition valve 20 to vaporize the injected fuel, and the EGR gas can be cooled using the latent heat of vaporization. When the amount of fuel injected into the exhaust gas recirculation passage 17 changes, the amount of heat taken by the fuel from the EGR gas changes, so that the EGR gas supply temperature can be adjusted by adjusting the fuel injection amount by the fuel addition valve 20. That is, the fuel addition valve 20 functions as an EGR gas temperature adjusting means according to the present invention.

  Further, the internal combustion engine 1 is provided with a variable capacity turbocharger 21 for supercharging. The turbocharger 21 includes a compressor 21a disposed in the intake passage 6 and a turbine 21b disposed in the exhaust passage 7 on the downstream side of the connection position 17a of the exhaust recirculation passage 17, and the compressor 21a, the turbine 21b, Are combined so that they can rotate together. The turbocharger 21 is further provided with a movable vane 21c as a movable member that is provided at the inlet of the turbine 21b and can be throttled by moving between the maximum opening and the minimum opening. Further, an intercooler 22 for cooling the pressurized air is provided in the intake passage 6 on the downstream side of the compressor 21a.

  As shown in FIG. 1, the exhaust gas recirculation device 16 is controlled by an engine control unit (ECU) 30 provided as a computer for appropriately controlling the operating state of the internal combustion engine 1. The ECU 30 includes a microprocessor and peripheral devices such as a ROM and a RAM necessary for its operation, and controls each part of the internal combustion engine 1 based on signals from various sensors. For example, the ECU 30 controls the fuel injection amount and the fuel injection timing by operating the fuel injection valve 5, controls the switching of the intake system by operating the on-off valve 15, and the opening degree of the movable vane 21 c of the turbocharger 21. Control or the like is executed according to the operating state of the internal combustion engine 1. As a sensor connected to the ECU 30, a signal corresponding to the temperature (intake air temperature) of the crank angle sensor 31 that outputs a signal corresponding to the engine speed (rotational speed) of the internal combustion engine 1 or the air flowing in the intake passage 6 is used. An output intake air temperature sensor 32 is provided. Various other sensors are connected to the ECU 30, but these are not shown because they are not related to the gist of the present invention.

  Hereinafter, the control executed by the ECU 30 in relation to the present invention will be described. FIG. 2 is a flowchart showing an example of a control routine for exhaust gas recirculation control executed by the ECU 30. The program of this routine is held in the ROM of the ECU 30, and is read out in a timely manner and repeatedly executed at a predetermined calculation interval. This control routine is executed in the case of the state through the one port described above. In step S1, the ECU 30 first acquires, for example, the engine speed Ne, the fuel injection amount Q, and the intake air temperature Ta as the operating state of the internal combustion engine 1. The engine speed Ne is acquired based on a signal from the crank angle sensor 31. As the fuel injection amount Q, a calculation result of fuel injection control (not shown) executed in parallel with FIG. 2 is used. The intake air temperature Ta is acquired based on a signal from the intake air temperature sensor 32. Next, in step S <b> 2, the flow rate (EGR amount) of EGR gas to be supplied into the cylinder 2 is calculated according to the operating state of the internal combustion engine 1. Next, in step S3, the ECU 30 controls the opening degree of the exhaust gas recirculation valve 18 so that the calculated EGR amount is obtained.

  Next, the ECU 30 obtains the temperature (EGR gas supply temperature) Tp of the EGR gas supplied to the cylinder 2 via the one port. Since the EGR gas supply temperature Tp changes in correlation with the exhaust temperature of the internal combustion engine 1 and the engine speed, it can be estimated based on the correlation specified in advance. It is also possible to provide a temperature sensor in the exhaust gas recirculation passage 17 and directly acquire it. Next, in step S5, a target temperature Ttrg for the EGR gas supply temperature Tp is set. This target temperature Ttrg is set so that the temperature difference between the EGR gas supplied to the cylinder 2 via the intake port 9 and the air supplied via the intake port 8 is within a predetermined range. It is set in consideration of the temperature of the air supplied via. The intake air temperature Ta acquired in step S1 is used as the temperature considered for setting the target temperature Ttrg. The setting of the target temperature Ttrg can be realized by preparing a map that gives the target temperature Ttrg using the intake air temperature Ta as a variable and referring to the map.

  Next, in step S6, it is determined whether the EGR gas supply temperature Tp is higher than the target temperature Ttrg. When the temperature Tp is higher than the target temperature Ttrg, the process proceeds to step S7, and when the temperature Tp is equal to or lower than the target temperature Ttrg, it is not necessary to execute the process of injecting fuel from the fuel addition valve 20 (cooling control). The processing is skipped and the current routine is terminated.

  In step S7, a fuel amount (fuel supply amount) q to be injected from the fuel addition valve 20 is calculated. The calculation is performed according to the following procedure.

  (1) First, a required temperature decrease amount ΔTp required for reducing the EGR gas supply temperature Tp to the target temperature Ttrg is calculated according to the difference between the EGR gas supply temperature Tp and the target temperature Ttrg.

  (2) Next, the maximum fuel supply amount qmax1 per unit amount of EGR gas is calculated based on the required temperature decrease amount ΔTp. When the amount of fuel injected from the fuel addition valve 20 increases, fuel that cannot be vaporized comes out, and the temperature drop amount of the EGR gas is not proportional to the fuel supply amount. Therefore, a map that specifies the upper limit of the fuel supply amount that can be completely vaporized with respect to the required temperature decrease amount ΔTp as the maximum fuel supply amount qmax1 is experimentally created and stored in the ROM of the ECU 30, and the ECU 30 stores the map. By referring to this, the maximum fuel supply amount qmax1 corresponding to the required temperature decrease amount ΔTp is calculated. FIG. 3 shows an example of the map. As shown in this figure, the maximum fuel supply amount qmax1 corresponding to the required temperature decrease amount ΔTp is calculated as one of the candidates for the fuel supply amount q.

  (3) Next, the maximum fuel supply amount qmax2 per unit amount of EGR gas is calculated based on the exhaust temperature Te of the exhaust gas taken out from the exhaust passage 7. The exhaust temperature Te is synonymous with the temperature of the EGR gas at the inlet of the exhaust gas recirculation passage 17, and is estimated based on the engine speed and load (fuel injection amount) of the internal combustion engine 1. The maximum fuel supply amount qmax2 is calculated as an upper limit value at which the injected fuel can be completely vaporized and does not self-ignite in the atmosphere of the exhaust temperature Te. Specifically, a map that gives the maximum fuel supply amount qmax2 as an exhaust temperature Te as a variable as shown in FIG. 4 is experimentally created and stored in the ROM of the ECU 30, and the ECU 30 refers to this map. The maximum fuel supply amount qmax2 is calculated as one of the candidates for the fuel supply amount q.

  (4) Next, based on the passage wall temperature Twa at the predetermined position a (see FIG. 1) of the exhaust gas recirculation passage 17, the maximum fuel supply amount qmax3 per unit amount of EGR gas is set as one of the candidates for the fuel supply amount q. calculate. Specifically, as in the case of (3), a map that gives the maximum fuel supply amount qmax3 with the passage wall temperature Twa as a variable as shown in FIG. 5 is experimentally created and stored in the ROM of the ECU 30. The ECU 30 refers to this map to calculate the maximum fuel supply amount qmax3 as one of the candidates for the fuel supply amount q. In this map, the maximum fuel supply amount qmax3 is given as an upper limit value that does not self-ignite even when vaporized fuel touches the passage wall of the exhaust gas recirculation passage 17. Similarly, as shown in FIG. 6, the maximum fuel supply amount qmax4 per unit amount of EGR gas is one of candidates for the fuel supply amount q based on the passage wall temperature Twb at another predetermined position b (see FIG. 1). Calculate as The passage wall temperatures Twa and Twb may be directly measured by a temperature sensor or may be estimated from a predetermined empirical formula. The number of predetermined positions is arbitrary, and candidates for the fuel supply amount q may be calculated based on the passage wall temperature relating to positions other than the positions a and b.

  (5) Finally, a minimum one of the maximum fuel supply amounts qmax1, qmax2, qmax3, and qmax4 calculated as a plurality of candidates for the fuel supply amount q is specified, and the EGR amount is specified as the specified maximum fuel supply amount. The fuel supply amount q is calculated by multiplying.

  After the fuel supply amount q is calculated as described above, in the subsequent step S8, the ECU 30 controls the fuel addition valve 20 so that fuel corresponding to the fuel supply amount q is injected from the fuel addition valve 20 this time. This routine ends.

  Since the EGR gas supply temperature Tp is adjusted to the target temperature Ttrg by repeatedly executing the control routine of FIG. 2, the temperature difference between the EGR gas supplied into the cylinder 2 and air becomes excessive. Can be prevented.

  Next, fuel supply prohibition control executed by the ECU 30 will be described with reference to FIG. FIG. 7 is a flowchart showing an example of a control routine of fuel supply prohibition control. The routine of FIG. 7 is repeatedly executed at predetermined intervals in parallel with the routine of FIG.

  In step S11, the ECU 30 first acquires the passage wall temperature Twa at the predetermined position a of the exhaust gas recirculation passage 17. In this embodiment, the passage wall temperature at the same position as described above is acquired, but the passage wall temperature at a position different from that position may be acquired. This passage wall temperature Twa can be obtained by the same method as described above. Next, in step S12, it is determined whether the passage wall temperature Twa is equal to or less than a predetermined value Twth. The predetermined value Twth is an upper limit value of the passage wall temperature at which vaporization may be insufficient, and is set experimentally. Accordingly, when the passage wall temperature Twa is equal to or lower than the predetermined value Twh, the fuel is insufficiently vaporized when the fuel is injected from the fuel addition valve 20, so that the process proceeds to step S13 so that the cooling control is prohibited. The operation of the fuel addition valve 20 is controlled so that fuel injection from the addition valve 20 is prohibited, and this routine is finished. On the other hand, if the passage wall temperature Twa is higher than the predetermined value Twh, it is not necessary to prohibit the cooling control, so step S13 is skipped and the current routine is terminated.

  According to the control of FIG. 7, fuel injection from the fuel addition valve 20 is prohibited when the passage wall temperature is equal to or lower than a predetermined value, so that fuel adhesion to the exhaust gas recirculation passage 17 is avoided. Thereby, clogging of the exhaust gas recirculation passage 17 can be avoided reliably.

  In the first embodiment, the ECU 30 executes the step S4 to step S10 in FIG. 2 to execute the step S9 in FIG. 2 as the EGR gas temperature control means according to the present invention. By executing the routine of FIG. 7 as the calculation means and the fuel supply amount calculation means, each functions as the fuel supply prohibition means according to the present invention.

(Second form)
Next, a second embodiment of the present invention will be described with reference to FIG. Hereinafter, description of the configuration common to the first embodiment is omitted. This embodiment is characterized in that the fluctuation of the combustion state of the internal combustion engine 1 accompanying the execution of fuel injection (cooling control) by the fuel addition valve 20 is suppressed. In this embodiment, the internal combustion engine 1 is configured to execute the pilot injection mode. That is, the internal combustion engine 1 can divide the fuel injection by the fuel injection valve into a main injection performed at a predetermined time and a pilot injection performed before that with a smaller amount of fuel than the main injection, and Each fuel injection timing and each fuel injection amount of main injection and pilot injection can be changed. Further, the internal combustion engine 1 is configured so that the fuel injection pressure by the fuel injection valve 5 can be changed.

  When the cooling control is executed, the fuel injected by the fuel addition valve 20 is vaporized and then supplied into the cylinder 2 together with the EGR gas. Therefore, before the fuel is injected into the cylinder 2 by the fuel injection valve 5, the fuel concentration in the cylinder 2 becomes high and the ignition timing in the compression stroke is advanced, and the cylinder is caused by the temperature difference between the EGR gas and air. 2 causes a fluctuation in combustion such as a change in the distribution of the air-fuel mixture formed in the fuel cell 2. As a result, there is a risk that harmful components in the exhaust gas may increase compared to the normal time when fuel is not supplied by the fuel supply means. Therefore, in this embodiment, the combustion fluctuation prevention control of FIG. 8 is executed together with the control of FIGS. 2 and 7 so that such combustion fluctuation does not occur.

  FIG. 8 is a flowchart showing an example of a control routine for combustion fluctuation prevention control. The program of this routine is held in the ROM of the ECU 30, and is read out in a timely manner and repeatedly executed at a predetermined calculation interval. First, in step S21, the ECU 30 determines whether cooling control is being executed. If the cooling control is being executed, the process proceeds to step S22. If not, the subsequent process is skipped and the current routine is terminated.

  In step S22, it is determined whether or not the EGR gas supply temperature Tp is within an allowable range including the target temperature Ttrg. If it is within the allowable range, the process proceeds to step S23, and early ignition prevention control is performed to prevent the ignition timing of fuel in the cylinder 2 from being advanced. In the early ignition prevention control, the ECU 30 executes at least one of an operation for reducing the fuel injection amount of the pilot injection and an operation for delaying the fuel injection timing of the main injection for the internal combustion engine 1. Since these operations have the effect of suppressing the early ignition timing, both of these operations may be executed simultaneously.

  When the EGR gas supply temperature Tp is out of the allowable range, the process proceeds to step S24 to determine whether or not the EGR gas supply temperature Tp is higher than the upper limit of the allowable range. If the EGR gas supply temperature Tp is higher than the upper limit, the process proceeds to step S25, and if not, the process skips step S25 and proceeds to step S26.

  In step S25, the ECU 30 executes distribution change prevention control. When the EGR gas supply temperature exceeds the upper limit of the allowable range, the relatively high temperature EGR gas is biased toward the center in the cylinder 2 due to the temperature difference between the EGR gas supplied to the cylinder 2 and the air. As a result, the temperature of the atmosphere in the center of the cylinder 2 rises, and the evaporation of the fuel spray injected from the fuel injection valve 5 is accelerated. For this reason, the air-fuel mixture hardly reaches the vicinity of the inner peripheral surface of the cylinder 2 and the distribution of the air-fuel mixture formed in the cylinder 2 changes. The distribution change prevention control is performed to prevent such a change in the mixture distribution. In this distribution change prevention control, the ECU 30 is at least one of an operation of increasing the fuel injection pressure by the fuel injection valve 5, an operation of reducing the fuel injection amount of the pilot injection, and an operation of retarding the fuel injection timing of the main injection. To the internal combustion engine 1. All of these operations have an effect of suppressing the change in the mixture distribution, and therefore all of these operations may be performed, or two operations selected from these operations may be performed.

  In step S26, the injection amount of the main injection is corrected in consideration of the fuel supply amount by the fuel addition valve 20, and the current routine is ended.

  According to the control of FIG. 8, the early ignition prevention control and the distribution change prevention control are appropriately executed according to the EGR gas supply temperature Tp to prevent the early ignition of the fuel in the cylinder 2 and the distribution change of the air-fuel mixture. Therefore, the combustion fluctuation in the cylinder 2 accompanying cooling control can be prevented.

  In the second mode, the ECU 30 functions as an EGR gas temperature control unit, a candidate calculation unit, a fuel supply amount calculation unit, and a fuel supply prohibition unit according to the present invention, as in the first mode, and step S23 in FIG. By executing step S25 of FIG. 8 as an early ignition prevention unit according to the present invention, each functions as a distribution change prevention unit according to the present invention.

(Third form)
Next, a third embodiment of the present invention will be described with reference to FIG. Hereinafter, description of the configuration common to the first embodiment is omitted. This embodiment is characterized in that the air is passed through the exhaust gas recirculation passage 17 by linking the operation of the exhaust gas recirculation valve 18 and the operation of the movable vane 21c of the turbocharger 21 under specific conditions after the execution condition of the cooling control is satisfied. There is. FIG. 9 is a flowchart showing a control routine of exhaust gas recirculation control according to the third embodiment. In addition, the same code | symbol is attached | subjected to the process same as FIG. 2, and description is abbreviate | omitted. As is apparent from FIG. 9, the control routine of this embodiment is obtained by inserting steps S31 to S32 between step S7 and step S8 in FIG. That is, when it is necessary to reduce the EGR gas supply temperature Tp, the ECU 30 determines whether the engine speed of the internal combustion engine 1 is decelerating and the fuel injection by the fuel injection valve 5 is interrupted (fuel cut) in step S31. Determine whether or not.

  Since combustion does not occur in the cylinder 2 when the fuel is cut, the air guided to the intake passage 6 is discharged to the exhaust passage 7 via the cylinder 2. Therefore, the air exhausted to the exhaust passage 7 can be guided to the exhaust recirculation passage 17 by controlling the opening of the exhaust recirculation valve 18 to the open side. Therefore, when the engine speed of the internal combustion engine 1 is decelerating and the fuel injection by the fuel injection valve 5 is interrupted, the routine proceeds to step S32, where the opening of the exhaust gas recirculation valve 18 is set to the opening side and fully opened. In step S33, the opening degree of the movable vane 21c is controlled so that the differential pressure between the inlet and the outlet of the exhaust gas recirculation passage 17 increases and the amount of air passing through the exhaust gas recirculation passage 17 increases. Controlling the opening of the movable vane 21c to the closed side to increase the back pressure, controlling the opening to the opening side to decrease the supercharging pressure, or the differential pressure between the outlet and the inlet of the exhaust gas recirculation passage 17 The degree of contribution differs depending on the operating state of the internal combustion engine 1. Therefore, in step S33, the opening degree of the movable vane 21c is controlled in the high direction in which more air flows through the exhaust gas recirculation passage 17 in accordance with the operating conditions of the internal combustion engine 1. For example, in the opening degree control of the movable vane 21c, a map in which the relationship between the opening degree of the movable vane 21c and the amount of air passing through the exhaust gas recirculation passage 17 is experimentally determined corresponding to various operating conditions is stored in the ROM of the ECU 30 This can be realized by searching the map for the opening degree of the movable vane 21c at which the amount of air passing through the exhaust gas recirculation passage 17 is maximized in the current operating state.

  According to the control of FIG. 9, the passage wall temperature can be lowered by allowing air to pass through the exhaust gas recirculation passage 17 without causing fuel to adhere to the passage wall.

  In the third mode, the ECU 30 functions as an EGR gas temperature control unit, a candidate calculation unit, and a fuel supply amount calculation unit according to the present invention, similarly to the first mode, by executing the routine of FIG. By performing Steps S31 to S33 in FIG. 9, the passage wall temperature control means according to the present invention functions.

(4th form)
Next, a third embodiment of the present invention will be described with reference to FIG. Hereinafter, description of the configuration common to the first embodiment is omitted. This embodiment is characterized in that fuel injection from the fuel addition valve 20 is performed intermittently. FIG. 10 is a timing chart showing the correspondence between the fuel injection by the fuel addition valve 20 and the lift of the intake valve in the intake stroke of each cylinder 2. # 1 to # 4 in FIG. 10 are cylinder numbers, and these correspond to the order in which the cylinders 2 are arranged from left to right in FIG. The fuel injection by the fuel addition valve 20 is divided into injection timings t1 to t4 and is intermittent. The time required for the EGR gas cooled by the fuel injection of the fuel addition valve 20 to reach the cylinder 2 is α. As is apparent from this figure, the fuel injection by the fuel addition valve 20 is performed so that the arrival time x1 when the EGR gas cooled by the fuel injection of the fuel addition valve 20 reaches the # 2 cylinder 2 is synchronized with the intake stroke. Time t1 is set. Similarly, the fuel injection timings t2 to t4 are set so that the arrival timings x2 to x4 are synchronized with the intake strokes of the other cylinders 2, respectively.

  Since the time α correlates with the engine speed of the internal combustion engine 1, a map for specifying the time α for each engine speed is experimentally created and stored in the ROM of the ECU 30, and the ECU 30 refers to the map. Thus, the time α corresponding to the engine speed can be calculated. Further, the intake stroke of each cylinder 2 can be specified by a signal from the crank angle sensor 31. As a result, the ECU 30 can control the fuel injection timing so that the arrival time and the intake stroke of each cylinder 2 are synchronized.

  According to this embodiment, since the EGR gas supplied to the cylinder 2 can be aimed and cooled, fuel injection by the fuel addition valve 20 becomes intermittent. That is, less fuel is wasted than when fuel is continuously injected between time t1 and time t4 in FIG. As a result, the amount of fuel consumed by the fuel addition valve 20 is suppressed, so that the EGR gas cooling efficiency is improved. This form of fuel injection can be applied to each of the forms described above.

The figure which showed the principal part of the internal combustion engine to which the exhaust gas recirculation apparatus which concerns on one form of this invention was applied. The flowchart which showed an example of the control routine of the exhaust gas recirculation control which concerns on a 1st form. The figure which showed an example of the map which gives the maximum fuel supply amount by making the required temperature fall amount into a variable. The figure which showed an example of the map which gives the maximum fuel supply amount by making exhaust gas temperature into a variable. The figure which showed an example of the map which gives the maximum fuel supply amount by making passage wall temperature into a variable. The figure which showed an example of the map which gives the maximum fuel supply amount by making into a variable the passage wall temperature of the position different from FIG. The flowchart which showed an example of the control routine of the fuel supply prohibition control which concerns on a 1st form. The flowchart which showed an example of the control routine of the combustion fluctuation prevention control which concerns on a 2nd form. The flowchart which showed an example of the control routine of the exhaust gas recirculation control which concerns on a 3rd form. The timing chart explaining a 4th form.

Explanation of symbols

1 Internal combustion engine 2 Cylinder 5 Fuel injection valve 6 Intake passage 7 Exhaust passage 8 Intake port (remaining intake port)
9 Intake port (some intake ports)
16 Exhaust gas recirculation device 17 Exhaust gas recirculation passage 18 Exhaust gas recirculation valve (regulating valve)
20 Fuel addition valve (EGR gas temperature adjustment means, fuel supply means)
21 Turbocharger 21a Compressor 21b Turbine 21c Movable vane (movable member)
30 ECU (EGR gas temperature control means, candidate calculation means, fuel supply amount calculation means, fuel supply prohibition means, early ignition prevention means, distribution change prevention means, passage wall temperature control means)

Claims (12)

This is applied to an internal combustion engine provided with a plurality of intake ports for one cylinder, and a part of the exhaust extracted from the exhaust passage of the internal combustion engine passes only through some of the intake ports. In the exhaust gas recirculation device for an internal combustion engine that can be supplied as EGR gas into the cylinder,
EGR gas temperature adjusting means capable of adjusting EGR gas supply temperature, which is the temperature of EGR gas supplied to the cylinder via only the partial intake port, and among the EGR gas supply temperature and the plurality of intake ports Target setting means for setting a target temperature of the EGR gas supply temperature so that a temperature difference from the temperature of the air supplied to the cylinder via the remaining intake port of the engine falls within a predetermined range; and the EGR gas An exhaust gas recirculation apparatus for an internal combustion engine, comprising: EGR gas temperature control means for controlling the EGR gas temperature adjustment means so that a supply temperature becomes the target temperature set by the target setting means . An exhaust gas recirculation passage connected to the exhaust passage for guiding EGR gas;
As the EGR gas temperature adjusting means, a fuel supply means capable of injecting fuel into the exhaust gas recirculation passage is provided,
The EGR gas temperature control means controls the fuel supply means so that fuel is injected into the EGR passage when the EGR gas supply temperature is higher than the target temperature. An exhaust gas recirculation device for an internal combustion engine as described.   The plurality of candidates for the fuel supply amount to be injected by the fuel supply means are set to the exhaust temperature taken out from the exhaust passage based on the required temperature decrease amount required to reduce the EGR gas supply temperature to the target temperature. Based on the passage wall temperature at a predetermined position of the exhaust gas recirculation passage, the fuel supply means injects the candidate calculation means for calculating each and the minimum value of the plurality of candidates calculated by the candidate calculation means. The exhaust gas recirculation device for an internal combustion engine according to claim 2, further comprising fuel supply amount calculation means for calculating the fuel supply amount to be calculated.   3. A fuel supply prohibiting means for controlling the fuel supply means so that fuel injection by the fuel supply means is prohibited when a passage wall temperature of the exhaust gas recirculation passage is a predetermined value or less. Or an exhaust gas recirculation device for an internal combustion engine according to 3. The internal combustion engine is configured as a compression ignition type engine having a fuel injection valve for injecting fuel into the cylinder,
When the EGR gas supply temperature is within the allowable range including the target value after the fuel injection by the fuel supply means is performed, the ignition timing of the fuel injected by the fuel injection valve is prevented from being advanced. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 2 to 4, further comprising early ignition prevention means for performing a predetermined operation that can be performed on the internal combustion engine. The internal combustion engine divides fuel injection by the fuel injection valve into main injection performed at a predetermined time and pilot injection performed before the predetermined time with a smaller amount of fuel than the main injection. And the fuel injection timing and the fuel injection amount of the main injection and the pilot injection can be changed.
The early ignition preventing means performs, as the predetermined operation, at least one of an operation of reducing the fuel injection amount of the pilot injection and an operation of retarding the fuel injection timing of the main injection for the internal combustion engine. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 5. The internal combustion engine is configured as a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into the cylinder,
When the EGR gas supply temperature exceeds the upper limit of the allowable range including the target value after the fuel injection by the fuel supply means is performed, evaporation of the fuel injected by the fuel injection valve is prevented from being accelerated. The exhaust gas recirculation apparatus for an internal combustion engine according to any one of claims 2 to 4, further comprising an early evaporation preventing unit that executes a predetermined operation that can be performed on the internal combustion engine. The internal combustion engine can change a fuel injection pressure by the fuel injection valve, and the fuel injection by the fuel injection valve is performed at a predetermined timing with a main injection and a smaller amount of fuel than the main injection than the predetermined timing. The pilot injection mode divided into pilot injection performed before can be executed, and each fuel injection timing and each fuel injection amount of the main injection and the pilot injection can be changed,
The early evaporation prevention means delays the fuel injection timing of the main injection and the operation of increasing the fuel injection pressure by the fuel injection valve, the operation of decreasing the fuel injection amount of the pilot injection, and the predetermined operation. The exhaust gas recirculation device for an internal combustion engine according to claim 7, wherein at least one of operations is performed on the internal combustion engine. The internal combustion engine is configured as a compression ignition type internal combustion engine having a fuel injection valve for injecting fuel into the cylinder,
An adjustment valve capable of adjusting the flow rate of the gas flowing through the exhaust gas recirculation passage, and the adjustment valve is controlled to open when the engine speed of the internal combustion engine is decelerating and fuel injection by the fuel injection valve is interrupted The exhaust gas recirculation apparatus for an internal combustion engine according to any one of claims 2 to 8, further comprising a passage wall temperature control means. The internal combustion engine includes a compressor provided in an intake passage including the remaining intake ports, a turbine provided in the exhaust passage downstream of a position where the exhaust recirculation passage is connected, and a maximum opening degree. A variable displacement turbocharger having a movable member capable of restricting an inlet of the turbine by moving between the minimum opening and the compressor and the turbine are combined so as to be integrally rotatable. And
When the engine rotational speed of the internal combustion engine is decelerating and fuel injection by the fuel injection valve is interrupted, the passage wall temperature control means opens the adjustment valve and closes the opening of the movable member. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 9, wherein the control valve and the movable member are respectively controlled so as to be on a side. The internal combustion engine includes a compressor provided in an intake passage including the remaining intake ports, a turbine provided in the exhaust passage downstream of a position where the exhaust recirculation passage is connected, and a maximum opening degree. A variable displacement turbocharger having a movable member capable of restricting an inlet of the turbine by moving between the minimum opening and the compressor and the turbine are combined so as to be integrally rotatable. And
When the engine speed of the internal combustion engine is decelerating and fuel injection by the fuel injection valve is interrupted, the passage wall temperature control means opens the adjustment valve and opens the opening of the movable member. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 9, wherein the control valve and the movable member are respectively controlled so as to be on a side.   The EGR gas temperature control means is configured so that the arrival time at which the EGR gas cooled by the fuel injected by the fuel supply means reaches the cylinder via the partial intake port is synchronized with the intake stroke of the cylinder. The exhaust gas recirculation device for an internal combustion engine according to any one of claims 2 to 8, wherein the fuel injection timing by the fuel supply means is controlled.

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